In general, a producer of synthetic resin or the like is required to check, as part of quality control, whether or not gel or fish eye is generated in the synthetic resin produced.
The manufacturer who obtains synthetic resin from the producer to manufacture various kinds of products is also required to check the resin thus obtained to see if there is fish eye or gel in the resin and to consider to what extent fish eye or gel is generated in the case where there is a predetermined condition of the work. This is because, if such fish eye or the like exists, an attempt to print on the surface of a product made with the synthetic resin will result in a defective product due to poor adhesion of ink to the surface.
A test roll apparatus is an apparatus for testing whether or not fish eye or gel is generated in synthetic resin.
The test roll apparatus has a pair of heating rolls disposed in parallel relationship. The pair of heating rolls is arranged such that the gap therebetween is freely adjustable and the direction and speed of the rotation are also freely adjustable. In addition, the temperature of the heating rolls may be variously set. The gap between the heating rolls may initially be set at, for example, 0.2 mm.
The heating rolls are used to make a resin testing sheet as follows:
A predetermined amount of a certain powdered resin is fed to a gap between the heating rolls. Since a small gap is formed between the pair of heating rolls, a very small part of the powdered resin would fall through the gap, but major part of the resin of the powdered resin forms a mound-like deposit rising from the gap.
The heating rolls are heated to a predetermined temperature and rotated at either the same rotational speed or at different rotational speeds to impart shearing force and thermal energy to the powdered resin on the heating rolls. As a result of the shearing, the powder of the resin itself also generates heat.
By the heat generated in the resin powder itself through shearing and also the heat imparted by the heating rolls, the resin is partly melted and extruded in the form of a sheet through the gap between the heating rolls, which is slightly widened. The leading end of the extruded sheet is advanced by the rotation of the heating rolls and the sheet is wound on one heating roll. As a result, melted or partly melted resin is wound on one of the pair of heating rolls. In addition, melted resin is deposited into the gap between the pair of heating rolls.
In this state, kneading is continued for a predetermined time period. With time, the size of the resin mound is decreased with a resultant increase in the width of the sheet wound on the heating roll. When the mound of melted resin is completely kneaded, the kneading by the heating rolls is stopped and the sheet of resin is separated from the heating roll.
In order to separate the sheet of resin, the sheet wound on the stopped heating roll is cut or severed parallel to the axis of the heating roll. Then the cut end of the sheet of resin is then pulled, while the heating roll is rotated, to separate the sheet of resin from the heating roll.
The sheet of resin thus produced by the test roll apparatus is used to look for gel or fish eye in the sheet of resin as follows:
The sheet of resin obtained as described above is tensioned by suitable means and light is shined on the back side of the sheet while the front side of the sheet is observed visually. If fish eyes or the like are present in the sheet of resin, they are seen as white lightened spots. Fish eyes or the like is measured by counting the white lightened spots and/or measuring the spot diameters with a slide caliper or rule.
The prior art test roll apparatus described above has required several manual operations, including those to cut a sheet of resin wound on a heating roll, mount the sheet of resin separated from the heating roll, and detect fish eyes or the like in the sheet of resin.
When manually cutting a sheet of resin wound on the heating roll, the operator has been required to work beside the heating roll which was not fully cooled. Thus, there was a danger that the operator would have been burned. In addition, manual sheet cutting has resulted in sheets of irregular shapes, with the disadvantageous result that sheets of resin having uniform dimensions could not be obtained.
Also, it has been troublesome to manually put the separated sheets of resin on a frame and frequently it has been impossible to put the sheets on the frame under uniform tension.
Moreover, when the sheet thus mounted was held to light and inspected to detect fish eyes, count their number, and measure their sizes, there has been the possibility of damage to the operator's eyes. Another big problem has been human error, with differences depending on the particular observers included in the measured data.
In the prior art, the thickness of a resin sheet wound on a heating and kneading roll was measured by first cutting a part of the wound resin sheet with a suitable device such as for example a spatula and then measuring the resin fragment thus obtained with a dial gauge.
However, the operation of manually cutting a part of the resin sheet from the heating and kneading roll during its rotation involved the danger that an operator be burned, have fingers pinched between the heating and kneading rolls, and so on. In addition, manual measurements with a dial gauge caused differences in the measured values of the thicknesses of sheets as between different operators who measured with the gauge.
In the conventional kneading apparatus, which includes the conventional test roll described above, the pair of heating rolls are arranged such that a gap between them is set to a predetermined dimension and the gap is then widened as the thickness of a sheet wound on a heating roll is increased. The heating rolls are rotated during a kneading operation in such directions that a bank or mound of the material is caught and pinched between the rolls.
The conventional kneading apparatus was run by an operator according to his own experience and perception. In the conventional kneading apparatus, therefore, the kneading operations cannot be said to have always been carried out in the best way. Different operators followed different kneading steps, with the result that the degree of kneading was not always constant.
With the conventional kneading apparatus, moreover, the width of a rolled sheet wound about one of the heating rolls (the one hereinafter called the "sheet winding roll") is increased with the kneading time. In order to assure a predetermined width of the rolled sheet, therefore, a pair of width limiting plates are provided on the peripheral surface of the sheet-winding roll. Each plate has a bottom end with a curved surface having the same radius as the sheet-winding roll.
The width limiting plates are only effective to limit the width of rolled sheets and in no way contribute to the kneading operation.
On the other hand, in the conventional kneading apparatus, a rolled sheet enters a bank formed in a gap formed between the sheet winding roll and the other heating roll (hereinafter called the "counter roll") disposed opposite to the sheet winding roll to achieve a kneading operation. In order to render the kneading operation efficient, controls are provided for adjustment of the relative speeds of the counter roll and the sheet winding roll, maintaining the temperatures of these rolls, and so on.
There are problems with the conventional kneading operation described above. The conventional kneading apparatus is not yet satisfactory in that kneading takes a long time and the kneading operation and widthwise offsetting of a rolled sheet are carried out independently. Thus, the kneading operation as a whole is troublesome.
In the production of a kneaded sheet with the conventional kneading apparatus, the heating rolls are heated to predetermined temperatures and rotated in the initial stage of the process of producing the kneaded sheet to apply heat and shearing force to a mound above a gap between the heating rolls, so that mound particles of powdered material are fused and united together and become partly melted. The material thus becomes appropriately fluid and begins to hang from the heating rolls through the gap therebetween.
When the part of the material hanging down through the gap between the heating rolls grows to a suitable length, the operator uses an appropriate tool such as knife, spatula, or the like to guide the part of the material hanging down through the gap between the heating rolls onto and along the peripheral surface of one of the heating rolls until the forward end portion of the hanging part of the material is guided to a point above the gap between the heating rolls.
The conventional kneading apparatus, which inevitably requires such manual operation, involves a danger that the operator pinches his hand or his hands in between the heating rolls.
Moreover, in such a conventional kneading apparatus, even though the gap between the heating rolls is set to a small dimension in the initial stage of kneading operation, the powdered material leaks and falls through the gap between the heating rolls resulting in a substantial loss of the powdered material.
In order to eliminate this loss of powdered material, one might think to dispose a receiving member under the pair of heating rolls to catch the material falling through the gap between the heating rolls and to return the fallen material to a point above the gap between the heating rolls. However, it is quite troublesome to each time dispose such a receiving member under the gap between the heating rolls, take out and lift the receiving member to the gap between the heating rolls, and drop the powdered material from the receiving member toward the gap between the heating rolls. If such operation is to be manually carried out by an operator, there is a danger that the heating rolls may burn the operator.
When the kneading by the heating rolls has proceeded to a certain extent, the end of the sheet of the material, which hangs down from the heating rolls, must be wound on a heating roll. In the past, this operation was also carried out manually. Therefore, there was a great danger that, when the sheet end was wound, the heating rolls would burn the operator.
In the case where the conventional kneading apparatus is used to manufacture a sheet of vinyl chloride resin, silicone resin, or the like, or a sheet of an elastic high molecular compound such as rubber or EPDM, the sheet must be removed from the sheet winding roll. Several methods are conceivable for removing such sheet from the sheet winding roll.
One method might be to first cut or sever the sheet of the material wound on the sheet winding roll by means of a scraper having a thin knife edge. However, it has been found that, when a sheet on the sheet winding roll is cut by the scraper, the cut end of the sheet becomes waved and fail to provide a removed sheet having a linear cut end. It has also been found that, when the scraper is urged against a sheet on the sheet winding roll in order to cut the sheet, the surface of the sheet winding roll is damaged by the edge of the scraper. Accordingly, measures for preventing the sheet winding roll from being damaged are required.
Another method is to cut open a sheet on the sheet winding roll parallel to its axis with a sharp knife.
However, it has been found that, with the method of using the knife, it is difficult to squarely and accurately cut open a sheet along the roll axis. In addition, there is a possibility that the knife damages the surface of the sheet winding roll, as in the case of the scraper. Thus, some measures are demanded for avoiding the damage.
In the past, moreover, because the scraper or the knife was manipulated by an operator to cut a sheet, there was a danger that the operator could be burned by the heat of a very high temperature heating rolls.
With the conventional kneading apparatus, it was required to clean the surfaces of the heating rolls after a sheet produced by kneading was removed from the heating rolls. The operator used a cloth to wipe the surfaces of the heating rolls to remove deposits of material such as synthetic resin or elastic high molecular weight compounds adhered to the heating rolls. However, there was a problem that the removing operation took a long time and lowered the operation rate of the kneading apparatus. In addition, because both heating rolls become substantially hot, there was a danger that the manual operation could involve burns.
The present invention was made in consideration of these circumstances.
Therefore, the present invention has as one object to provide a sheet testing apparatus which automatically detects or measures fish eyes, gel, and so on that are present in a sheet of resin, without requiring any manual operation.
It is another object of the present invention to provide a frame which can be easily charged with a sheet of resin obtained by severing a rolled sheet of resin wound on a kneading roll that also acts as a heating roll and which is easily used with a means for detecting foreign matter to test the resin sheet.
It is a further object of the present invention to provide a sheet testing sample-making apparatus which easily and automatically makes a sheet testing sample which is charged with a sheet of resin and which can be easily mounted on a foreign matter detecting means for detecting foreign matter in sheets of resin.
It is a further object of the present invention to provide a frame feeding apparatus to feed a frame to kneading rolls so that the frame can be suitably used for making the sheet testing sample and so that a rolled sheet wound on the kneading roll can be automatically mounted on and applied to the frame.
It is a still further object of the present invention to provide an automatic sheet thickness detecting apparatus which is operative to automatically, safely and accurately measure, without requiring any manual operation, a sheet formed by heating and kneading rolls.
It is a still further object of the present invention to provide an automatic kneading apparatus which kneads a material uniformly.
It is a still further object of the present invention to provide a kneading apparatus which kneads material efficient and which simultaneously performs both kneading and widthwise adjustment of a rolled sheet.
It is a still further object of the present invention to provide a kneading apparatus which kneads efficiently.
It is a still further object of the present invention to provide a kneading apparatus and a fallen material returning apparatus used therewith which effectively returns, to a point above a gap between heating rolls, material fallen through the gap between the heating rolls.
It is a still further object of the present invention to provide a kneading apparatus and a fallen material returning apparatus used therewith which are operative to automatically return, to a point above a gap between heating rolls, powdered material dropped through the gap between the heating rolls in an initial stage of kneading operation to thereby reduce loss of the powdered material.
It is a still further object of the present invention to provide a kneading apparatus and a fallen material returning apparatus used therewith which are operative to automatically return, to a point above a gap between heating rolls, powdered material dropped through the gap between the heating rolls in an initial stage of kneading operations to thereby reduce loss of the powdered material and which also automatically wind on a heating roll an end of a sheet of the material hanging down through the gap between the heating rolls in a later stage of the kneading operation.
It is a still further object of the present invention to provide a roll cutting apparatus which is operative to sever, without any manual operation, a rolled sheet wound on a sheet winding roll to form an accurately linear cut end and which does not damage the surface of the sheet winding roll.
It is a still further object of the present invention to provide a heating roll cleaning apparatus which is operative to automatically clean the surfaces of a pair of heating rolls to improve the rate of operation and assure safety.